High temperature processing in dyedeveloper diffusion transfer systems



United States Patent HIGH TEMPERATURE PROCESSING IN DYE- DEVELOPER DIFFUSION TRANSFER SYSTEMS Richard W. Becker, Rochester, N.Y., assiguor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Dec. 12, 1967, Ser. No. 689,779 Int. Cl. G03c 7/00 US. Cl. 96-3 Claims ABSTRACT OF THE DISCLOSURE Processing of dye developer diffusion transfer system in presence of a bis-benzothiazolium salt wherein two benzothiazolium salt groups are joined by a long chain alkylene group results in increased densities at elevated temperatures.

This invention relates to the art of photography and more particularly to a dye diffusion transfer process in photography and materials adapted for use in the process.

A diffusion transfer color process has been described in a number of patents, including British Patent 804,971, published Nov. 26, 1958, wherein photographic elements containing silver halide emulsion layers and layers containing diifusible dye developers (dyes having a silver halide developing function) are exposed to record the latent image in the silver halide and then treated with an alkaline processing composition which permeates the emulsion layers and layers containing the dye developers which then develop the latent images to silver images. At the same time oxidation products of the dye developers are formed in situ with the silver images and which are relatively nondiffusing in the colloid vehicle of the layers.

The non-diffusing character of the oxidized dye developers is apparently due at least in part to a decrease in solubility in the alkaline processing liquid, and may also be due to a hardening effect of the oxidized developer upon the colloid vehicles of the layers which retards the diffusion of the oxidized dye developers. The residual unoxidized dye developers remaining in the layers in imagewise distribution are transferred by diffusion to a superposed reception element substantially to the exclusion of the silver image and oxidized dye developer to provide a positive dye image.

When an element containing differentially sensitized silver halide emulsion layers is used and subtractively colored dye developers are present in or contiguous to the respective emulsion layers, upon treatment with the processing liquid the dye developers are oxidized and rendered non-diffusing in the developed regions of the layers and the residual dye developer images in the positive regions are transferred by diffusion and in register to the reception element to provide a multicolor reproduction.

In the above described dye developer diffusion transfer process, an alkaline processing composition is utilized partly to initiate the development of the emulsion layers and also to act as a medium through which the unoxidized dye developer images and other substances diffuse to and from the receiving layer. The processing composition is usually spread in limited quantity between the surface of the light-sensitive or negative element and a mordanted receiving sheet. It is therefore desirable to include in the processing composition a thickening agent which increases the viscosity thereof, particularly for in-camera processing wherein the processing composition is utilized in a rupturable pod or like container.

When in-camera processing is conducted, the temperature of processing will, of course, depend upon the prevalent ambient temperature. Such temperatures can vary over a wide range. Thus, ambient temperatures as high as 3,502,467 Patented Mar. 24, 1970 "Ice F. or above may be encountered, for example, in desert or tropical regions.

It has been observed in dye developer diffusion transfer processes that when the dye developer images are transferred to the reception element from the sensitive elements under conditions of elevated temperature, the images tend to have less density than desired and, less density than would be expected from the quantity of dye developer available for transfer. This results in reduced maximum densities and a generally inferior product. Since increases in temperature will increase the rate at which the silver halide is developed, it has been proposed to employ various stabilizing agents in the system for the purpose of shortening the time of development. However, the inclusion of such materials has not resulted in a photographic product having satisfactory maximum densities at elevated temperatures. Additionally, some of these compounds have not been satisfactory since they are overoperative at room temperature, e.g., 72 F. and cause a prematurely short time for development of the silver halide at such lower temperatures.

Accordingly, it is an object of this invention to provide an improved dye developer diffusion transfer system.

A further object of this invention is to provide an improved dye developer diffusion transfer system for use at elevated temperatures.

It is still another object of this invention to provide an improved dye developer diffusion transfer process characterized by producing dye developer images having improved maximum densities at elevated temperatures.

These and other objects of the invention are accomplished by processing photographic elements containing at least one photographic silver halide emulsion layer and a dye developer contiguous to the silver halide of the silver halide emulsion layer in the presence of a his benzothiazolium salt wherein two benzothiazolium salt groups are joined, at the respective heterocyclic nitrogen atoms thereof, by a long chain alkylene group. As used herein and in the appended claims, -long chain alkylene refers to a divalent hydrocarbon group containing at least 6 but less than about 35 carbon atoms. An alkaline processing solution is utilized to initiate development and a dye developer image is transferred to a dye developer reception layer. Upon application of the alkaline processing solution to the exposed photographic element, the silver halide in the regions of exposure is developed and the contiguous dye developers are immobilized, Thereafter, dye developers from the unexposed and undeveloped areas of the photographic element diffuse and are transferred in register to a reception layer to form positive dye developer images.

Surprisingly, it has been found that dye developer diffusion transfer elements can be processed at elevated temperatures and still yield transferred images having satisfactory maximum densities, if the element is processed in the presence of a bis-benzothiazolium salt wherein two benzothiazoli-um salt groups are joined, at the respective heterocyclic nitrogen atoms thereof, by a long chain alkylene group. Typical useful bis-benzothiazolium salts are represented by the general formula wherein R represents a hydrogen atom or a lower alkyl group, .such a methyl, ethyl, etc. (e.g., an alkyl group containing from 1-2 carbon atoms), D represents the non-metallic atoms necessary to complete a benzene nucleus as well as substitution products thereof, including such member substituted by methyl, ethyl, methoXyl, ethoxyl, etc., 11 represents a positive integer of from 626, and X represents an acid anion, such as perchlorate, bromide, benzenesulfonate, toluenesulfonate, methyl su1- fate, ethyl sulfate, etc.

Although processing of dye developer diffusion transfer systems at elevated temperatures ordinarily results in an unsatisfactory reduction in maximum densities, the long chain bis-'benzothiazolium salts of the present invention act as controlled development restrainers in such systems and permit the attainment of high maximum densities at elevated temperatures. During processing with the alkaline solution, the development restrainers of the present invention inhibit development of unexposed silver halide. The restraint of development of the silver halide results in more dye developer being available for diffusion into the receiving layer. Thus, the maximum density of the print is increased without substantially increasing the minimum density. Additionally, the development restrainers of the present invention have the highly desirable characteristic of having no significant effect on the systems at ordinary room temperatures, i.e., about 70 F., while becoming effective at those temperatures above ordinary room temperatures, e.g., between about 85 and 130 F.

Representative long chain bis-benzothiazolium salts include:

Hexamethylene-bis-benzothiazolium perchlorate U CH HC Heptamethylene-bis-benzothiazolium perchlorate Nonamethylene-bis-benzothiazolium perchlorate Decarnethylene-bis-benzothiazolium perchlorate N C H2) Decamethylene-bis-(2-methylbenzothiazolium) perchlo- Decamethylene-bis-2-methylbenzothiazolium bromide Decamethylene bis 6 methoxybenzothiazolium perchlorate CH HO I H2)1o N C104 C104 Hexacosane-l,26-bis-benzothiazolium perchlorate Still other suitable long chain bis-benzothiazolium salts include:

Decamethylene-bis-benzothiazolium benzenesulfonate,

Decamethylene-bis-benzothiazolium toluenesulfonate,

Decamethylene-bis-benzothiazolium methyl sulfate,

Decamethylene-bis-benzothiazoliurn ethyl sulfate,

Undecamethylene-bis-benzothiazolium bromide,

Tetradecamethylene-bis-benzothiazolium perchlorate, and

the like.

These compounds have been previously described in the prior art. Many of the compounds represented by the generic formula, above, are described and can be prepared according to the methods described in Wilson U.S. Patent No. 2,425,774, issued Aug. 19, 1947, as well as by the method described by Allen and Wilson U.S. Patent No. 2,694,716, issued Nov. 16, 1954, the disclosures of which are hereby incorporated by reference. Such methods generally comprise the fusion of a heterocyclic base with an alkylene halide. Such techniques are Well known to those skilled in the art.

The long chain bis compound of the present invention is provided in the dye developer system of the present in- 'vention in such a manner that it is present during processing at elevated temperatures as an active development restrainer. The long chain salt is preferably utilized in one or more of the layers of the photosensitive element, e.g., the silver halide emulsion layer, although it may be provided in the image-receiving element or in the alkaline processing composition.

The concentration of salt effective to restrain high temperature development varies over a wide range. Concentrations should be increased with higher processing temperatures. Generally, between about 0.005 and about 0.1 g./Ag mole, preferably between about 0.015 and about 0.03 g./Ag mole is suitable to achieve satisfactory maxiinum Fdensities at elevated temperatures, such as The long chain bis-benzothiazolium salts of the present invention can be incorporated into any hydrophilic colloid layer of the photosensitive element, e.g., the silver halide emulsion layer, the dye-developer layer, an interlayer, etc., as an aqueous solution, an alcohol-water solution, or by any other manner known in the art.

Dye developers are well known in the photographic art. Such compounds function both as a silver halide developing agent and as a dye in photographic difi-usion transfer systems. Dye developers are characterized as bemg relatively nonditfusible in colloid layers such as the hydrophilic organic colloids used in photographic emul- 810118 at neutral pH, but diffusible in the photographic elements in the presence of alkaline processing solutions. Generally, such dye developers are substantially insoluble in water, which property usually necessitates the use of organic solvents to incorporate the dye developers into the organic colloid layers of the photo-elements. The dye developers are particularly characterized as containing both a chromophoric or dye moiety and at least one moiety having a silver halide developing agent function. Particularly useful dye developers are those wherein the chromophoric moiety as an azo or anthraquinone dye moiety and the silver halide developing moiety is a benzenoid moiety such as a hydroquinonyl moiety.

Representative dye developers of use in the dispersions of the invention have the general formula MN=N--D in which M is an aromatic or heterocyclic ring or ring system such as a benzene, naphthalene, tetralin, anthracene, anthraquinone, pyrazole, quinoline, etc., ring which can be substituted with such groups as hydroxyl, amino, keto, nitro, alkoxy, aryloxy, acyl, alkylamido, alkylaryl, carboxamido, sulfonamido, carboxyl or sulfo groups. D represents a silver halide developing agent moiety, imparting the developing agent function to the dye developer such as a hydroquinonyl group which can be substituted with amino, alkylarnino, alkyl, hydroxyl, alkoxyl or halogen groups.

Typical useful dye developers are described in U.S. Patents 3,146,102 and 3,161,506 as well as elsewhere in the patent literature, including: Australian 220,279; German 1,036,640; British 804,971 and 804,973-5; Belgian 554,935; French 1,168,292; and Canadian 577,021 and 579,938.

In the photographic elements useful in the invention, the dye developers are preferably incorporated in hydrophilic organic colloidal vehicles or carriers comprising the layers of the photographic element dissolved in high-boiling or crystalloidal solvents and dispersed in finel -divided droplets. Typical high-boiling, Water-insoluble solvents that can be used to dissolve dye developers in preparing the dispersions of the invention are described in U.S. Patent 2,322,027.

The dye developers utilized in the photographic elements useful in the invention can also be incorporated into vehicles soluble in organic solvents which are also solvents for the dye developers. Likewise, other incorporating techniques for the dye developers such as ball-milling can be utilized.

The dye developers are utilized contiguous to the silver halide of the photographic silver halide emulsion layers of the present photographic elements. Such dye developers can be incorporated directly in the silver halide emulsions or preferably positioned in a sublayer contiguous to each silver halide emulsion layer. The contiguity of the dye developer with respect to the silver halide can take the form of a mixed packet system wherein the dye developer can be present in a matrix surrounding a particle or globule containing silver halide grains. The dye developers are preferably substantially complementary in color to the color of the light recorded or spectral sensitivity of the silver halide emulsions contiguous thereto.

A wide variety of colorless hydroquinone derivatives can be utilized in the dye developer diffusion transfer sys tems of the invention. Such colorless hydroquinone derivatives are substantially insoluble in water and ditfusible in the hydrophilic organic colloids comprising the present photographic elements in the presence of alkaline processing compositions. Typical suitable colorless hydroquinone derivatives are listed in U.S. Patent 3,146,102 and are preferably employed in one or more layers of the light-sensitive element.

A wide variety of diifusible onium compounds can also be utilized in the present invention. Such onium compounds, that is, compounds that contain an organic cation, are diifusible in the hydrophilic organic colloids comprising the present photographic elements in the presence of alkaline processing compositions. Such onium compounds are typically quaternary ammonium compounds, quaternary phosphonium compounds or tertiary sulfonium compounds. A particularly useful class of onium compounds are heterocyclic quaternary ammonium compounds that are capable of forming diffusible methylene bases in alkaline processing compositions such as those described in U.S. Patent 3,146,102. In dye developer diffusion transfer system-s, the onium compounds are preferably utilized in the alkaline processing composition, although the onium compounds can also be utilized in the reception sheet, or less desirably, in one or more layers of the light-sensitive element, or in at least two of such positions.

Water-soluble silver halide solvents can be employed in the alkaline processing compositions used in the dye developer transfer process of the invention, particularly in conjunction with onium compounds and colorless hydroquinone derivatives as described above, such addenda lending further improvement in color quality results. Preferred silver halide solvents are thiosulfates such as sodium, potassium and ammonium thiosulfate.

The silver halide emulsions utilized in preparing photographic or light-sensitive elements used in the present diffusion transfer systems can be any of the conventional negative-type, developing-out emulsions. Typical suitable silver halides include silver chloride, silver bromide, silver bromoiodide, silver chloroiodide, silver chlorobromoiodide and the like. Mixtures of more than one of such silver halides can also be utilized. In accordance with usual practice, such silver halide emulsions can contain spectral sensitizers, hardeners, coating aids, plasticizers, antifoggants and the like conventional emulsion addenda.

In preparing such silver halide emulsions, as well as in preparing the various layers of photographic elements used in the present dilfusion transfer process, including the layers containing the dye developers, and colorless hydroquinone derivatives, mordant-containing reception layers, interlayers, topcoat layers and the like, a wide variety of hydrophilic organic colloids can be utilized as the vehicle or carrier. Gelatin is preferably used as the hydrophilic colloid or carrier material although such material as polyvinyl alcohol and its water-soluble derivatives and copolymers, water-soluble copolymers such as polyacrylamide, imidized polyacrylamide, etc., and other water-soluble film-forming materials that form waterpermeable coats such as colloidal albumin, water-soluble cellulose derivatives, etc., can be utilized in preparing the photographic elements. Compatible mixtures of two or more of such colloids can also be utilized.

The various layers utilized in preparing the diffusion transfer photographic elements used in the process of the invention can be coated on a wide variety of photographic supports. Typical supports include cellulose nitrate film, cellulose acetate film, polyvinyl acetal film, polystyrene film, polyethylene terephthalate film, polyethylene film, polypropylene film, paper, polyethylenecoated paper, polypropylene-coated paper, glass and the like.

Similarly, a wide variety of receiving sheets can be utilized to receive the transfer images from the photographic elements. Typical reception layers for receiving sheets include such materials as linear polyamides, proteins such as gelatin, polyvinyl pyrrolidones, poly-4-vinyl pyridine, polyvinyl alcohol, polyvinyl salicylal, partially hydrolyzed polyvinyl acetate, methyl cellulose, regenerated cellulose, or mixtures of such. These reception layers can be coated on a suitable support of the type described above for the light-sensitive elements of the invention and including transparent as well as opaque supports. Also, receiving sheets that release acidic material such as that derived from an acidic polymer or other acidic compound as a controlled rate as are described in U.S. Patent 2,584,030 are particularly useful. Such acidic materials are typically positioned in layers on the receiving sheet below the dye developer reception layer, there suitably being a spacer layer between the acid layer and the mordanting layer to control the release of acidic material. Such acidic materials serve to neutralize residual portions of the alkaline activator on the receiving sheet. A wide variety of nonditfusible cationic or basic dye-mordanting compounds can be used in liquid permeable reception layers including amines such as polymeric amines, quaternary ammonium compounds, quaternary phosphonium compounds and tertiary sulfonium compounds. Such mordants are nondiffusible in the alkaline processing composition and contain at least one hydrophobic ballast group. As described above, either or both of the onium compounds and colorless hydroquinones can be incorporated on the receiving sheets. As previously mentioned, the long chain bis-benzothiazolium salts of the present invention may also be provided in the reception element.

Light-sensitive elements containing integral reception layers for dye developer images can also be utilized. Such integral reception layers can be coated beneath the emulsion and dye developer layers near the support. A stripping layer coated over the integral reception layer can be used to facilitate the removal of the over-coated layers after the ditfusion of the dye developer images to the reception layer.

The processing compositions or activators used to initiate development of the exposed light-sensitive elements in accordance with the invention are strongly alkaline. The bis-benzothiazolium salts of the invention can be incorporated in these processing compositions. Such processing compositions generally have a pH of at least 12 or contain at least .01 N hydroxyl ion. Alkali metal hydroxides, such as sodium hydroxide, and sodium carbonate, are advantageously used in the composition for imparting such high alkalinity. However, volatile amines such as diethyl amine can also be used, such amines having the advantage of being volatilized from the prints to leave no residue of alkali. As mentioned previously, due to the unstable character of the hydroquinone derivatives in strong alkali, the colorless hydroquinone derivatives are preferably not used in the processing composition although when the pyridinium salts are present improved results are obtained. Such processing compositions are generally aqueous liquids or solutions, and, as previously mentioned, when utilized in rupturable pods for in-camera processing such as described in US. 'Patent 2,435,717, generally contain thickening agents such as hydroxyethyl cellulose or carboxymethyl cellulose. Thickened processing compositions typically have viscosities of at least 5,000 cps. to 100,000 or even 200,000 cps.

The production and use of photosensitive products containing the development restrainer compounds of the present invention are illustrated in the following examples.

EXAMPLES 13 A sensitive element is prepared by coating a subbed film support comprising cellulose acetate with suitably hardened genatin layers as follows:

(1) Cyan dye developer layer An aqueous gelatin containing the cyan dye developer 5,8-dihydroxy-1,4-bis[(fl hydroquinonyl c methyl) ethylamino] anthraquinone is dissolved in a mixture of N-n-butylacetanilide, 4-methyl cyclohexanone and dispersing agent Alkanol B. The mixture is passed through a colloid mill several times, coated on the subbed support and dried so as to volatilize the 4-methyl cyclohexanone.

(2) Red-sensitive emulsion layer A gelatino silver bromoiodide emulsion layer, which is sensitized to the red region of the spectrum is coated upon the cyan dye developer layer.

(3) Interlayer A gelatin interlayer is then coated on the red-sensitive emulsion layer.

(4) Magenta dye developer layer An aqueous gelatin solution containing the magenta dye developer 2[p-(2',S-dihydroxyphenethyl) phenylazo]-4-n-propoxy-1-naphthol is dissolved in a mixture of cyclohexanone, N n-butylacetanilide and Alkanol B is passed through a colloid mill several times, coated on the interlayer and dried to volatilize the cyclohexanone.

(5) Green-sensitive emulsion layer A green-sensitive silver bromoiodide emulsion is coated on the magenta layer.

(6) Interlayer A second gelatin interlayer is coated onto the greensensitive emulsion layer.

(7)Yellow dye developer layer An aqueous gelatin solution of the yellow dye developer, 1 phenyl-3-N-n-hexylcarboxamido-4-[p-2,5' dihydroxyphenethyl)-phenylazo]-5 pyrazolone, is dissolved in a mixture of ditetrahydrofurfuryl adipate, ethylene glycol monobenzyl ether, and Alkanol B, is passed through a colloid mill several times. The resulting dispersion is chilled to set it, washed to remove ethylene glycol monobenzyl ether followed by coating upon the second interlayer and drying.

(8) Blue-sensitive emulsion layer A blue-sensitive silver bromoiodide emulsion is coated onto the yellow dye developer layer.

(9) Overcoat layer A final gelatin emulsion overcoat layer containing 4'- methylphenylhydroquinone is provided on the foregoing layers.

A sample of the freshly coated film is exposed under a step tablet through red, green and blue filters and is processed at a temperature of 12 F. with a processing solution disposed in a processing pod and having the composition set forth in Table 1 below:

TABLE 1 Percent by weight Hydroxyethyl cellulose (Hercules type 250, high viscosity 3.5 Sodium hydroxide 4.5 Benzotriazole 2.0 l-phenethyl-Z-picolinium bromide 2.0

The exposed film is processed at a gap of 0.004 inch (corresponding to the thickness of the activator layer) in contact with a color receiving sheet. The receiving sheet is a white pigmented cellulose acetate butyrate support carrying a gelatin layer containing a mixture of poly-4-vinyl pyridine mordant and 1-phenyl-5-mercapto tetrazole. The cyan, magenta and yellow dye developer images transfer from the undeveloped regions to the receiving sheet.

The foregoing procedure is repeated with the exception that 20 milligrams of decamethylene-bis-benzothiazolium perchlorate is incorporated into each of the photosensitive silver halide emulsion layers 2, 5 and 8, respectively. The procedure is repeated a second time employing 40 milligrams of decamethylene-bis-benzothiazolium perchlorate instead of 20 milligrams. The maximum densities of each of the exposed negatives are set forth below in Table 2.

A comparison of the maximum print densities obtained while processing a negative comprising dye developers at the elevated temperature of 120 F. indicates that higher maximum densities may be achieved if processing is conducted in the presence of the long chain bis-benzothiazolium salts of the present invention.

The following examples illustrate the effectiveness of the development restrainers of the present invention as compared with conventional stabilization agents in a dye developer diifusion transfer system.

EXAMPLES 418 A monochromatic dye developer photosensitive element is prepared by coating a subbed film support comprising cellulose acetate with suitably hardened gelatin layers as follows.

(1) Magenta dye developer layer An aqueous gelatin solution containing the magenta dye developer 2[p-2,5-dihydroxyphenethyl)-phenylazo]- 4-n-propoxy-l-naphthol is dissolved in a mixture of cyclohexanone, N-n-butylacetanilide and Alkanol B is passed through a colloid mill several times, coated on the subbed support and dried to volatilize the cyclohexanone.

(2) Green-sensitive emulsion layer A green-sensitive silver bromoiodide emulsion is coated on the magenta layer.

(3) Overcoat layer A gelatin emulsion overcoat layer containing 4'-methylphenylhydroquinone is provided on the foregoing silver halide layer.

Samples of the freshly coated film are exposed under a green filter and are processed at temperatures of about 72 F. and 110 F., respectively, with a processing solution disposed in a processing pod and having the composition set forth in Table 1 above.

The exposed films are processed at a gap of 0.004 inch in contact with color receiving sheets similar to those of the previous examples. The magenta dye developer images transfer from the undeveloped regions to the receiving sheets. This procedure is repeated for comparative purposes while employing various stabilizing agents and the long chain salts of the present invention in the magenta dye developer layer of each negative. The results are set forth below in Table 3.

TABLE 3 A D max m8: Conc. at 70 F.- Example (g./Ag Dmax at No. Additive mole) 110 F 4 40 5 Decamethylenebis-benzo- 0. 010 33 thiazolimn perchlorate. 6 d 020 l6 -hydroxy-(Hnethyl-1,2,3,3a,7- 4. 0 55 pentazaindenc. -thioctic acid 4. 0 44 9 6-hydroxy-4-methyl-1,3,3a,7- 4. 0 37 tetrazaindcne. 2,4-dihydroxy-G-methyl-l,321,7- 4. 0 49 triazaindene. l-phenyl-5-mercaptotetrazole. 0.010 42 do 0.020 .40 Ammonium chloropalladate 0. ()3 46 do 0.06 .44 5-chlore-1,2,3-benzotriazole 0. 03 56 do. 0.06 .44 17 Benzothiazole-methiodide. 0. 02 58 18 o 0. 04 37 A comparison of the results set forth in Table 3 indi cates that the smallest loss in maximum density due to increasing temperature is obtained with the long chain development restrainer of the present invention; and that satisfactory maximum densities at increased temperatures are not obtainable with conventional stabilizers. Furthermore, a comparison of the maximum densities of Examples 4, 5 and 6 indicates that the effect on development of the compounds of the present invention is relatively small at room temperature whereas it has a very substantial effect at higher temperatures where it is needed.

The foregoing examples illustrate that satisfactorily high maximum densities may be obtained under relatively high temperature processing conditions. The employment of the long chain bis-benzothiazolium salts are not only useful for in-camera processing of exposed dye developer negatives, where the temperature of processing is controlled by the prevailing weather conditions, but the present salts may be employed in dye developer diffusion transfer systems whenever it is desired to increase the rate of processing by increasing the processing temperature and still achieve satisfactory maximum densities.

The invention has been described in considerable detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. In a process for producing a photographic transfer image which comprises processing an exposed photosensitive element comprising at least one light-sensitive silver halide emulsion layer, and a dye developer which is both a silver halide developing agent and a dye contiguous to the silver halide of said silver halide emulsion layer, said processing being effected by treating said photographic element with an alkaline solution, developing a latent image in the regions of exposure of said silver halide layer and thereby immobilizing said dye developer in said regions of exposure, dye developer in undeveloped regions diffusing imagewise in register to a dye developer reception layer, the improvement which comprises effecting said processing in the presence of a bis-benzothiazolium salt wherein two benzothiazolium salt groups are joined, at the respective heterocyclic nitrogen atoms thereof, by a long chain alkylene group.

2. The process of claim 1 wherein the photosensitive element comprises superposed red, green and blue lightsensitive silver halide emulsion layers and a dye developer contiguous to the silver halide of each of said layers.

3. The process of claim 2 wherein said bis-benzothia zolium salt has the formula:

] O-R R- III-(01312) X wherein R represents a member selected from the group consisting of a hydrogen atom and a lower alkyl group; D represents the non-metallic atoms necessary to complete a benzene nucleus; n represents a positive integer gen atoms thereof, my a long chain alkylene group.

4. The process of claim 2 wherein said bis-benzothiazolium salt is a decamethylene-bis-benzothiazolium salt.

5. The process of claim 2 wherein processing is conducted at a temperature in excess .of about 70 F.

6. The process of claim 2 wherein the processing is conducted at a temperature between about and about F.

7. The process of claim 3 wherein said bis-benzothiazolium salt is incorporated in said photosensitive element, prior to processing, at a concentration of from about .005 to about .1 gram per mole of the silver in said silver halide emulsion layer.

8. A photographic element comprising at least one light-sensitive silver halide emulsion layer, and a dye developer which is both a silver halide developing agent and a dye contiguous to the silver halide of said silver halide emulsion layer, said element having incorporated in at least one hydrophilic colloid layer thereof a bisbenzothiazolium salt wherein two benzothiazolium salt groups are joined, at the respective heterocyclic nitrogen atoms thereof, by a long chain alkylene group.

9. A photographic element of claim 8 which comprises superposed red, green and blue light-sensitive silver halide emulsion layers and a dye developer contiguous to the silver halide of each of said layers.

10. A photographic element of claim 8 wherein said bis-benzothiazolium salt has the formula:

wherein R represents a member selected from the group consisting of a hydrogen atom and a lower alkyl group; D represents the non-metallic atoms necessary to complete a benzene nucleus; n represents a positive integer of from 6 to 26; and, X represents an acid anion.

11. A photographic element of claim 8 wherein said bis-benzothiazolium salt is a decomethylene-bis-benzothiazolium salt.

12. A photographic element of claim 8 wherein said bis-benzothiazolium salt is present at a concentration of from about .005 to about .1 gram per mole of the silver in said silver halide emulsion layer.

13. A photographic product composed of a photosensitive element comprising at least one light-sensitive silver halide emulsion layer and a dye developer which is both a silver halide developing agent and a dye contiguous to the silver halide of said silver halide emulsion layer, a dye developer reception layer, said photosensitive element and said dye developer reception layer being capable of being superposed .on each other, and a bis-benzothiazolium salt wherein two benzothiazolium salt groups are joined, at the respective heterocyclic nitrogen atoms thereof, by a long chain alkylene group, said salt being so positioned in said product as to be present during the processing of said photosensitive element.

14. The photographic product of claim 13 wherein said bis-benzothiazolium salt has the formula:

wherein R represents a member selected from the group consisting of a hydrogen atom and a lower alkyl group; D represents the non-metallic atoms necessary to complete a benzene nucleus; n represents a positive integer of from 6 to 26; and X represents an acid anion.

15. The photographic product of claim 13 wherein said bis-benzothiazolium salt is provided in the photosensitive element.

16. The photographic product of claim 13 wherein said bis-benzothiazolium salt is a decamethylene-bis-benzothiazolium salt.

17. The photographic product of claim 13 wherein said bis-benzothiazolium salt is in said reception layer.

18. The photographic product of claim 13 which includes a rupturable container containing said salt and an alkaline processing composition for initiating development of said photosensitive element after exposure thereof.

19. The photographic product of claim 18 wherein said bis-benzothiazolium salt has the formula:

wherein R represents a member selected from the group consisting of a hydrogen atom and a lower alkyl group; D represents the non-metallic atoms necesary to complete a benzene nucleus; n represents a positive integer of from 6 to 26; and, X represents an acid anion.

20. The photographic product of claim 18 wherein said bis-benzothiazolium salt is a decamethylene-bis-benzothiw zolium salt.

References Cited UNITED STATES PATENTS 2,403,927 7/1946 Kendall et al. 96-109 XR 2,673,149 3/1954 Carroll 96-103 2,694,716 11/1954 Allen et al. 96--l04 XR 3,148,062 9/1964 Whitmore et al. 96-55 3,189,453 7/1965 Herz et al. 96-61 3,206,310 9/1965 Herz 96--67 3,342,596 9/1967 Graham 9650 NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICO, Assistant Examiner U.S. Cl. X.R. 9655, 66.3

my UNITED STATES PATENT omen:

CERTIFICATE OF CORRECTION Patent No- 31502 146] Dated March 214., 1970 Inventofls) Richard w. cker It is certified that error appear-l in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

I "1 In column 10, line 57, delete en atoms thereof, my a long chain alkylene group 7 an insert ---of from 6 to 26; and, X represents an acid anion.---

smm'mu 4, MALE" r it!" $EP29197U swmmmmm Aweau 'f wmxm x. mm. m. Atteltmg Officer Gemissiam 01' Patent: 

